Oral Presentation 24th Australian Conference on Microscopy and Microanalysis 2016

Composition and strain measurement in III-V semiconductors using convergent-beam electron diffraction under a  3-beam condition (#132)

Yueming Guo 1 , Philip NH Nakashima 1 , Joanne Etheridge 1 2
  1. Department of Materials Engineering, Monash University, Melbourne, Victoria, Australia
  2. Monash Centre for Electron Microscopy, Monash University, Melbourne, Victoria, Australia

Accurate local composition and strain measurement for III-V semiconductors such as InxGa1-xAs, AlxGa1-xAs and AlxIn1-xAs is critical to the development of many new technologies such as next generation transistors and laser diodes. EDX or S/TEM images can be powerful methods for composition OR strain measurement but it is challenging, if not impossible, to measure both simultaneously [1]. Furthermore, EDX and quantitative STEM have limited accuracy unless all the relevant experimental parameters are measured rigorously, which is very labour intensive.

Here we develop a method using convergent beam electron diffraction (CBED) to measure composition, thickness and strain simultaneously from the same specimen volume of a III-V semiconductor. The method uses a carefully chosen crystal orientation that optimises the influence of scattering from the chemically-sensitive {200} atomic plane. Composition, strain and thickness measurements are made from different features in the same CBED pattern. By virtue of the electron scattering processes involved, these features are generated by effectively different physical processes, so that the strain, composition and thickness measurements are essentially independent of each other. This offers the potential to relate composition directly to strain - measured in-situ from the same, nanoscale specimen volume - as opposed to deducing one from the other via Vegard’s law.

We demonstrate the accuracy and feasibility of the method on the InxGa1-xAs system using calculations and experiment.

Acknowledgements

The authors thank the Monash Centre for Electron Microscopy for facilities and staff support. This work was supported by the Australian Research Council grant number DP150104483.

  1. 1. Rosenauer, A., Transmission Electron Microscopy of Semiconductor Nanostructures: Analysis of Composition and Strain State, in Springer Tracts in Modern Physics,. 2003, Springer Berlin Heidelberg,: Berlin.